Vacuum distillation of crude c alcohols



May 6, 1958 K. R. BARNARD omwm INVENTOR.

KENT R. BARNARD BY )ai Arron/v5? United vStates Patent() VACUUMDISTILLATION CRUDE C ALCOHOLS Kent R. Barnard, Tulsa, Okla., assigner toPan American Petroleum Corporation, a corporation of DelawareApplication August 13, 1954, Serial No. 449,679 s anims. (cl. 2oz- 52)The present invention relates to a novel method for the separation ofalcohols from mixtures thereof containing ltetoncs which eitherazeotrope with. or which boil close to the boiling point of suchalcohols. More particularly, it pertains to a method for separatingvarious of the arnyl alcohols from ketones which either azeotropetherewith such as, for example, cyclopentanone, 2-methylcyclopentanoneand 3-methylcyclopentanone (hereinafter referred to asmethylcyclopentanones), or which -boil so close to the boiling point ofsaid various amyl alcohols that separation by means of straightfractional distillation is impossible.

lvfixtures containing 1-pentanol, Z-methyl-l-butanol and3-n1ethyl--1-butanol or at least one of these alcohols, together with atleast one of the aforesaid ketones can'- not be satisfactorily separatedby means of ordinary fractional distillation methods owing to the factthat Z-methyll-butanol and SLmethyl-l-butanol, which boil at l28.9 C.and 132 C., respectively, form azeotropes with cyclopentanone (B. P.130.7 C.) boiling at approximately 127.0 C. and 129.5a C, respectively,while the methylcyclopentanones, which boil at 13S-145 C., cannot beseparated from l-pentanol boiling at 138 C. Although the problem ofseparating various of the abovementioned amyl alcohols fromcyclopentanone or methylcyclopentanoncs occurs in numerous purificationprocedures, one of the principal instances where an .emcient method forthe separation of these compounds is most urgently needed is in theirrecovery, along with other chemicals, lfrom both the water and oilfractions producedI by the reduction of carbon monoxide with hydrogen inthe presence of a fluidized alkali-promoted iron catalyst under knownsynthesis conditions. The magnitude of this problem may be more fullyappreciated when it is realized that in hydrocarbon synthesis plantsdesigned for commercial operation and having a capacity of about 6,000barrels per day of liquid hydrocarbons, there are produced inthe waterstream alone approximately 4200 pounds of amyl alcohols per day andabout 1,000 pounds per day of cyclopentanone and methylcyclopentanones.Both classes of these compounds are found inthe oil stream in evengreater amounts than they normally occur in the aqueous fraction.Speciically, mixtures of these alcohols and ketones obtained from thewater stream usually contain from about 8 to 15 percent cyclopentanone,6 to l0 percent methylcyclopentanones, 40 to 5 0 percent l-pentanol, 7to 10 percent Z-methyl-l-butanol and 8 to 11 percent 3-methyl-1-butanol,together with about 15 to 25 percent of a high-boiling residue, 40 to 50percent of which consists of various carbonyl fractions.

y Attempts have previously been made to separate the above-mentionedamyl alcohols from one another and from the aforesaid ketones bydistilling a crude mixture containing these alcohols and ketones up to atemperature of about 87 C. Thereafter, a second fraction boiling fromabout 87 C..to about. 138C.,was collected, after which the resultingdistillatewas azeotropically distilled with ywater until the overheadbeing obtained was :substantially free of ketones. ADistillation ofthemixture under such conditions yielded a bottoms of l-pentanol and anoverhead fraction containing 2-methyl-1-butanol` and 3-methyl-1-butanol,cyclopentanone, methylcyclo-` pentanones and asmall amount of 1pentanol.This overhead fraction was distilled until all vof the water'had beenremoved, after which the resulting dry mixture of alcohols and ketoneswas subjected to distillation under a pressure of about 40 mm. Bythis'operation, however, a sizable fraction boiling from about 54 C. toabout 62 C. was obtained whichk contained the bulk of the with a largeportion of theketones which passedV overhead along with the alcohols. Inorder vto effect a sep aration between these alcoholsandketones, thedistillate t collected at 54 C. to 62 C. (40 mm.) vwas subjected todistillation at atmospheric pressure whereby there were obtained twooverhead fractions; one boiling'at 130 C. and the other boiling at-about'.138 C. to 140 C. The bottoms fraction was-relatively small andconsistedessentially of high-boiling ketone polymers. TheV aforesaidvfraction boiling at about 130 C. contained approximately p Likewise,efforts have been made to separate the aforesaid C5 alcoholsfrom oneanother and from said ketones by rst topping up to a temperature of`about `C; a crude mixture of` they alcohols and ketones to removelow-boiling components. Thereaftenzthe resulting residue was subjectedto.distillation and the overhead collected up to ay temperature of about13S-140 C. By this means, the higher boiling impurities present in theoriginal mixture were removed as bottoms. The voverhead fractionVreferred tov contained essentially normal and branched-chain C5"alcohols, cyclopentanone, andthe methylcyclopent-anones. To. separatethe branched-chain alcohols from the l-pentanol, the overhead wassubjected to fractionation andthe portion boiling A'from about 120-134vC. collected. Although this fraction was thought` to contain only thebranched C5 alcoholsand cyclopentanone, it was found .thatcyclopentanone also tended to take over with Vit some 1-pentanolfwhilethe branched-chain C5 alcohols carried along'fappreciable amounts ofmethylcyclopentanones. Consequently, under such circumstances,separation and purificationof-the desired components in said crudemixture by the above` mentioned procedure. was found to be impossible.

Accordingly, it is yan object of my invention to pro# yields from suchmixtures in substantially pureform.

Another object of my invention is to provide aprocess for the separationof l-pentanol, 2-methyl-1-butanol and S-methyl-l-butanol from mixturescontaining ketones'f` atV least some of which azeotrope with l-pentanoland some of which azeotrope. with Z-methyl-lfbutanoland3-methyl-lbutanobwhich process involves the Inaintenance of a`sufficiently concentration of `branched C alcohols in `thefractionation zoneduring the `initial distillation .hols` and` ketonecomponents in 'mixtures of` the type mentioned :abovecan be recovered in`a highly purified condition.` In-accordancelwith one embodiment of myinventiomta'mixture oflC5i3alcohols and close-boiling ketones,'ifromwhich `both lowand high-boiling imp urities have `been removed, issubjected to distillation in an elicient fractionation `column `atreduced pressure and' at a ,temperaturefsucientlyhigh at the prevailingpressure to removei `all of the ketone component overhead. i' In doing`so,'some'of `the branchedlchain C5 alcohols are taken'overhead as` anarrow-boiling mixture with the ketone fraction. .However, `with theexception of a very small percentage,a1l of the l-pentanolwhich, ingeneral, is theprinicipal component of such mixtures, is recovered inthebottoms fraction, together with branched C5 alcohols;A The latter maythenbe separatedy from the lpentanol relatively easily and inlsubstantially pure form by distillation `of the mixture at atmosphericpressure.

.Pressures `employed during the above-mentioned distillationmaygenerally range-from about `to about 100 f mm; atythettop of thetower. Corresponding temperatures required for these pressures rangefrom about 50 to about 80? Ci; usually,` I prefer to employ atemperature of from about "55 to about 65 C. and a pressure of fromabout 45` to about 55 mm. Ordinarily, substantially higher Apressuresthan Ythose .just `recited are considered undesirablefto'einploy at thisstage of the process because of therelatively high bottoms temperaturerequired to bring the` desired components overhead. Moreover, theazeotropes :involvedin such operation are leaner` with respect toketones` at the higher pressures. Also, higher temperatures,particularly over extended periods of'time,

l tendtoyconvertr thev ketones present into undesirable polymericproducts. l .The overhead from the aforesaid distillation operationistfurtherfractionatedat. top tower pressures of from aboutl30 toiabout100 andvapor `temperatures of fromabout 45 to about 75 l C., preferablyat pressures of from about.45 ,to-about 5S mm. and at temperatures of`from aboutSS to about 60 C. `This feed material, which lconsistsessentially of afnarrow-boiling mixture of ketonesvandbranched-cliain C5 alcohols, on fractionation l to about 500 and` atvapor .temperatures` of from about 100?" to about `115 lC.,"to yieldanroverhead containing principally branched C5` alcohols, generallytogetherwith` small amounts of methylcyclopentanones and l-pentanol.;'Ihel bottoms `fraction. .from this last-mentioned distillation stepconsistsessehtially of methylcyclo- Pentanones. W '4 The `division ofbranched-chainC5 alcohols" between the bottoms and distillatejin thevacuum distillationstep first mentionedjcan be V:controlledby 'thepressure employedand the `proportionofthe branched C5 alcohols toketonestimthe; feed to this operation. l'Ihus, if an excess of `branchedC5 alcohols is maintained'over the 4ratio required by the branched C5alcohol-methylcyclopentanone azeotropes, the branched C5 alcohols can beforced into the bottoms fraction with the 1-pentanol and laterfractionated therefrom at atmospheric pressure to yield individual cutsof substantially pure l-pentanol and branched C5 alcohols. Therefore,the greater the excess of branched C5 alcohols in the feed, the lessvacuum will be required for a satisfactory separation of the desiredmaterials. Utilizing this phenomenon, I may take the overhead fractionfrom the aforesaid methylcyclopentanones recovery step which is rich inbranched C5 alcohol and combine this `stream with the feed to theinitial vacuum distillation step. In this manner, a relatively highconcentration of branched C5 alcohols within the vacuum distillationcolumn is assured which, in turn, enables substantially complete removalof the ketone component into the overhead while additional branched C5alcohols coming in with the fresh feed are forced into the bottoms alongwith l-pentanol, as previously indicated. This result is made possiblebecause the composition of the aforesaid recycle stream with respect tobranched C5 alcohols is maintained at a substantially constant value.

The process of my invention may be further illustrated by the followingspecific example:

EXAMPLE A crudevmixture from which low-boiling impurities such as, forexample l-butanol, had been removed, having the following composition,was selected to be puri- The aboveV mixture is processed in accordancewith the scheme shown inthe accompanying llow diagram wherein saidmixture is introduced through line 2 into an intermediate section offractionating column 4, at an hourly rate of 1000 pounds; Column 41soperated at a top tower pressure of 800 mm. and a vapor temperature ofabout 133 C. Under these conditions, all components of the mixture, withthe exception of the C5 and heavier alcohol fraction, which is withdrawnfrom the system through line 5 at the rate of 160 pounds per hour, aretaken overhead through line 6 and condenser 8 with a portion of thisstream being returned as reux to the column through line 10. p The bulkof the overhead, however, is transferred through line 12 `to column 14,operated at a top tower pressure of 50 mm., Vand at a vapor temperatureof about 60 C. Under the conditions at which column 14 is operated, a C5alcohols fraction containing both branched and normal C5 alcohols andhaving less than .5 weight percent of ketone impurity is withdrawnthrough line` 16` at the rate of about 688 pounds per hour. 1- pentanolmay be `recovered in substantially pure form by subjecting this C5alcoholsI fraction to distillation at atmospheric pressure. The overheadfrom the operation of column 14 is taken off through line 18 andcondenser 20 with a portion of this stream being returned to the columnthrough line 22. This overhead fraction contains 84 pounds ofcyclopentanone, 72 pounds of methylcyclopentanones, 40 pounds of 2- and3-methyl-1-butanol and 5 pounds of l-pentanol.l Such mixture istransferred through line 24 to column 26vat the rate of 201 pounds perhour. Column 26 is likewise operated at reduced pressure, the top towerpressure being 50 mm. and the vapor temperature being 56 C. By operationof column 26 under 'these conditions, substantially pure cyclopentanoneis withdrawn through line 28 and condenser 30 at the rates of about 84pounds per hour. A small rellux of this stream to the tower ismaintained via line 32, while the balance of the product cyclopentanoneis removed through line 34. The bottoms fraction from this operation isremoved from column 26 through line 36 at a rate of 117 pounds per hourand introducedinto column 38 which is operated at a top tower pressureof about 500 mm. and at a vapor temperature of about 115 C. The bottomsproduct from this distillation operation, which is withdrawn from line40 at the rate of 68 pounds per hour, consists essentially of themethylcyclopentanones and is substantially free from Calcohols. Overheada stream is taken through line 42 and condenser 44, a portion thereofbeing returned to the column through line 46 as reux, and the balance,amounting to 49 pounds per hour, being combined with the feed to column14 in line 12 via line 48. This overhead stream transported through line4S contains 4 pounds ofmethylcyclopentanones, 40 pounds of 2- and3-methyl-1-butanol and about 5 pounds of l-pentanol. By recycling thisoverhead stream to column 14, it will be seen that I am able to maintaina relatively constant concentration of branched-chain C5 alcohols in thefractionation zone of said column. As a result of the creation of suchconditions in column 14, substantially all newly added C5 alcoholscoming into the system through line 2 are forced into the bottomsfraction of column 14 and removed therefrom by means of line 16. Suchconditions also provideffor the substantially complete removal ofmethylcyclopentanones as a bottoms fraction in column 38. f

While the foregoing description of the accompanying flow diagramillustrates advantageous embodiments of my invention, it is to beunderstood that the scope thereof is not necessarily limited thereto. Onthe contrary, my,`

invention is to be construed broadly lwith respect to the descriptionand to the claims; and, in general, it is to be understood that anymodification or equivalentswhich would naturally occur to those skilledin the art are to be considered as lying Within the scope of myinvention.

Thu-s, if desired, the fundamental features of my invention may beemployed in processing mixturesv of the type contemplated herein withoutrstl separating the lowand high-boiling contaminants from the compoundswhich it is desired to recover. Under such circumstances, the higherboiling impurities Would be secured along with 1- pentanol in thebottoms from the first vacuum distillation step. This bottoms fractionmay then be separately processed, for example by ordinary fractionation,to recover the l-pentanol therefrom. The overhead from the initialvacuum distillation operation, in addition to con,- tainingbranched-chain C5 alcohols, cyclopentanone and methylcyclopentanone,carries with it W-boiling impurities, as Well as small amounts ofentrained high-boiling cyclic ketones. These ketones appear with themethylcyclopentanones, as produced in accordance with my process, andthe methylcyclopentanones may be separated therefrom by subjecting themixture to ordinary fractionation, preferably at reduced pressure, i.e., at from about 30 to about 100 mmpand temperatures of from about 50to about 90 C. The low-boiling impurities gowith the cyclopentanonefraction and are separated therefrom by further distillation undersuperatmospheric pressure, i. e., 1500 to 2000 mm. at 140 to 150 C.

Throughout the present description and claims, the expressionclose-boiling ketones as used hereinv is'intended to include bothketones which azeotrope with the alcohol or alcohols concerned or whichboil so close thereto that separation cannot be effected by ordinarydistillation techniques. Likewise, the expression narrow-boiling mixtureis intended to cover both close-'boiling rmixtures and azeotropicmixtures of the alcohols and ketones concerned.

I claim:

l. In a process for the recoveryof l-pentanol, 2-methyl-l-butanol andS-methyl-l-butanol from a crude mixture containing close-boiling ketonesand wherein both lowand high-boiling impurities if originally present insaid mixture have been removedtherefrom, the steps which comprisesubjecting said mixture to fractionation in a distillation zone at apressure ranging from about 30 to about 100 mm. and at a temperature offrom about 50 to about C. to take overhead substantially all of saidclose-boiling ketones in the form of a narrow-boiling mixture with asubstantial portion of said Z-methyl-l-butanol and 3-methyl-1-butanoltogetherv with a minor amount or" l-pentanol and withdrawing as bottomsa mixtureA of 1- pentanol, Z-methyl-l-butanol and 3-methyl-l-butanolsubstantially free from said ketones, thereafter removing the bulk ofsaid ketones from the alcohols in the abovementioned overhead bysubjecting the latter to fractional distillation at a pressure rangefrom about 300 to about 800 mm. at vapor temperatures of-from about toabout C. and combining the resulting alcohol-rich overhead mixture withthe feed to said lirst-mentioned fractionation step whereby an excess ofalcohols in said zone is maintained over that requiredl to forceoverhead substantially all of the ketones in said crudefmixture.

2. The process of claim l in which the iirst-mentioned fractionationstep is effected at a pressure of from about 45 to about V55 mm., and ata temperature ranging from about 55 to about 65 C.

3. In a process for the recovery of l-pentanol, 2-methyl-l-butanol, andS-methyl-l-butanol from a mixture containing cyclopentanone andmethylcyclopentanones and wherein both lowand high-boiling impurities iforiginally present in said mixture have been removed therefrom, thesteps which comprise subjecting said mixture to fractionation in adistillation zone at a ypressure ranging from about 30 to about 100 mm.and at a temperature of from about 50 to aboutl 80 C. to take overheadsubstantially all of said cyclopentanone and methyllcyclopentanones inthe form of a narrow-boiling mixture with a substantial portion'ofsaidZ-methyl-l-butanol and S-methyl-l-butanol together with a yminoramount of 1-pentanol and withdrawing as bottoms a mixture of l-pentanol,Z-methyl-l-butanol and vB-methyl-l-butanol substantially free fromcyclopentanone and methylcyclo'- pentanones, thereafter subjecting theabove-mentioned overhead to further `distillation at reduced pressuresranging from about 30 to about 100 mm.' and at temperatures ranging fromabout 45 to about 75 to secure overhead substantially purecyclopentanone, subjectingthe bottoms fraction from the last-mentioneddistillation, which fraction contains essentially methylcyclopentanonesand 2 and B-methyl-l-butanols, to further distillation at a pressure.ranging from about 300 to about 800 mm. and at a temperature rangingfrom about 100 to about 130 C. to obtain a bottoms fraction ofmethylcyclopentanones substantially free from l-pentanol,Z-methyl-l-butanol and 3-methyl-l-butanol and an overheadV containingprincipally said 2- and 3-methyl-l-butanols and minor amounts ofmethylcyclopentanones and' l-pentanol, .and combining saidlast-mentioned overheadwiththe feed to said first-mentionedfractionation step'. whereby an excess of alcohols in said zone ismaintained over that required to force overhead substantially all oftherketones in said crude mixture. n' Y 4. The process of claim 3 inwhichthe,first-mentioned vacuum fractionation step is eiiected atpressures ranging from 45-to about 55 mm. and vapor temperatures of fromabout 55 to about 65C. and wherein the secondmentioned vacuumfractionation is carried out at pressures ranging from 45 to about 55mm. and at vapor temperatures of from about 55 to about 60 C.

5. The process of claim 1 in which said mixture is de rived from thesynthesis of hydrocarbons by the reduction of carbon monoxide withhydrogen in theA presence `of a hydrocarbon synthesis catalyst.

6. The process of claim 3 in whichy said mixture is derived from thesynthesis of hydrocarbons by the reduction of carbon monoxide ,withhydrogen.

7. In a process for the separation of 1-pentanol, 2-

purities and l-pentanol, 2-methyl-1-butanol and 3-methyl-v l-butanoL,`thereafter subjecting the above-mentioned overhead to furtherdistillation at reduced pressures ranging from about() to about 100 mm.and at temperatures ranging fromabout 40 to about 70 C. to secureoverhead cyclopentanoneand saidlow-boiling impurities, subjectinglthebottoms `fraction from said last-mentioned distillatiomwhich tractioncontains essentially said 2- and 3-methyl-l-butanols,` said entrainedhigh-boiling ketones, Aand methylcyclopentanones, to furtherdistillationat a pressure ranging from about300 to about 800mm.

. and at a temperature ranging fromabout 100 to about 130 C. to `obtaina bottoms'ffraction of methylcyclopentanones and said entrainedhigh-boiling cyclic ketones and an overhead containing principally` said2- and 3-methyll-butanols and minor amounts of saidmethylcyclopentanones,` and combining said last-mentioned overhead withthe feedto said first-mentioned fractionation step whereby an excess ofalcohols intsaid zone ismaintained over that required toforce overheadsubstantially all ofV the ketoncs in said crude mixture.

8. In a process for the separatonand purification of 1- pentanol and atleast one `of the alcohols,i2methyl1 butanol and 3-methyl-l-but`anol,from a4 crude mixture containing cyclopentanone andy isomericmethyl-cyclopentanones and wherein both low-and high-boiling impuri-`ties `if, originally present `in `said mixture have been removedtherefrom, the `steps which `comprise subjecting saidmixture tofractionation in a distillation zone at a pressure ranging `from about30v to about 100 mm. and

at a temperature of from labout 50 to about 80 C., to i take=overlieadsubstantially Hall of said cyclopentanone and isomericmethylcyclopentanones in the form of a.

narrow `boilingrmixture with a substantial portion of at least one ofsaid alcohols together with a minor amount of l-'pentanol andwithdrawing as bottoms a mixture ot l-'pentanol and at least one of saidalcohols substantially free `from said cyclopentanone andmethylcyclopentanones, thereafterremoving the bulk of said cyclopenta-`none from the alcohols in the above-mentioned overhead by subjectingthe latter to fractional distillation at a pressure ranging from about30 to about 100 mm. at vapor temperatures of from about 45 to about 75C., subjecting the bottoms fraction from the last mentioneddistillation, which fractionation contains essentiallymethylcyclopentanones and at least one of said alcohols, to yfurtherdistillation at a pressure ranging from about 300 to about 800 mm. andat a temperature ranging from about 100 i to. about 130 C., to obtain abottoms fraction of methylcyclopentanones substantially free from saidalcohols and l-pentanol and an overhead containing principally at leastone of said alcohols and minor amounts of methylcyclopentanones and1-pentanol, and combining the resulting alcohol richl overhead mixturewith the feed to said rst mentioned. fractionation step whereby yanexcess of at least one of said alcohols in said zone is maintained overthat required to force overhead substantially all of said cyclopentanoneand methylcyclopentanoncs in said crude mixture. l

References Cited in the tile of this patent UNITED STATES PATENTS2,324,255 Britton et ral July 13, 1943 12,551,584 Carlson et al May 8,1951 2,551,593 t Gilliland et al May 8, 1951 2,552,911 Steitz May l5,1951 2,564,200 AGrekel Aug. 14, 1951 2,568,522 l Stritz Sept. 18, 1951 i2,571,151 McGrath et al.l Oct. 16, 1951 2,617,757 Michael Nov. 11, 19522,635,072 Eliot Apr. 14, 1953 2,642,388 Steitz June 16, 1953 2,647,861Drout` Aug. 4, 1953

1. IN A PROCESS FOR THE RECOVERY OF 1-PENTANOL, 2-METHYL-1-BUTANOL AND3-METHYL-1-BUTANOL FROM A CRUDE MIXTURE CONTAINING CLOSE-BOILING KETONESAND WHEREIN BOTH LOW- AND HIGH-BOILING IMPURITIES IF ORIGINALLY PRESENTIN SAID MIXTURE HAVE BEEN REMOVED THEREFROM, THE STEPS WHICH COMPRISESUBJECTING SAID MIXTURE TO FRACTIONATION IN A DISTILLATION ZONE AT APRESSURE RANGING FROM ABOUT 30 TO ABOUT 100 MM. AND AT A TEMPERATURE OFFROM ABOUT 50* TO ABOUT 80*C. TO TAKE OVERHEAD SUBSTANTIALLY ALL OF SAIDCLOSE-BOILING KETONES IN THE FORM OF A NARROW-BOILING MIXTURE WITH ASUBSTANTIAL PORTION OF SAID 2-METHYL-1-BUTANOL AND 3-METHYL-1-BUTANOLTOGETHER WITH A MINOR AMOUNT OF 1-PENTANOL AND WITHDRAWING AS BOTTOMS AMIXTURE OF 1PENTANOL, 2-METHYL-1-BUTANOL AND 3-METHYL-1-BUTANOLSUBSTANTIALLY FREE FROM SAID KETONES, THEREAFTER REMOVING THE BULK OFSAID KETONES FROM THE ALCOHOLS IN THE ABOVEMENTIONED OVERHEAD BYSUBJECTING THE LATTER TO FRACTIONAL DISTILLATION AT A PRESSURE RANGEFROM ABOUT 300 TO ABOUT 800 MM. AT VAPOR TEMPERATURES OF FROM ABOUT 100*TO ABOUT 130C. AND COMBINING THE RESULTING ALCOHOL-RICH OVERHEAD MIXTUREWITH THE FEED TO SAID FIRST-MENTIONED FRACTIONATION STEP WHEREBY ANEXCESS OF ALCOHOLS IN SAID ZONE IS MAINTAINED OVER THAT REQUIRED TOFORCE OVERHEAD SUBSTANTIALLY ALL OF THE KETONES IN SAID CRUDE MIXTURE.